1. Field of the Invention
This invention relates to pH-dependent sustained release, drug-delivery composition, and, more particularly, to an effective composition which is characterized by including about 20 to 40% by weight of sodium alginate, about 4 to 12% of propylene glycol alginate (PGA), and about 40 to 80% of a pharmaceutical medicament.
2. Description of the Prior Art
U.S. Pat. No. 4,792,452 described a controlled release pharmaceutical formulation was described which released a pharmaceutical of a basic character at a controlled rate regardless of the pH of the environment. The formulation included a basic pharmaceutical, up to about 45% by weight of a pH dependent polymer, which was a salt of alginic acid, such as sodium alginate, and up to 35% by weight of a pH-independent hydrocarbon gelling agent such as hydroxypropylmethyl cellulose, in a 2% solution.
Many other references have described similar formulations in tablet form using a single alginate salt or combinations of salts.
Accordingly, it is an object of this invention to provide a pH-dependent sustained release, drug-delivery composition capable of being formed into tablets or pellets which includes a diffusion barrier formed by the interaction of a pH-dependent gelling material and a pH-independent non-gelling material.
A feature of the invention is the provision of such a composition which will provide a dissolution rate of about 20% of the drug within about 2 hours at acid pH, while the remaining 80% of the drug is released within at least 10 hours at alkaline or neutral pH, preferably 100% of the drug over a period of 12 hours.
What is described herein is a pH-dependent sustained release, drug delivery composition capable of being formed into tablets or pellets, wherein the release is controlled by a diffusion barrier formed by the interaction of a pH-dependent gelling material and a pH-independent non-gelling material, comprising a polymer matrix which includes, by weight, (a) 10 to 50% sodium alginate, (b) 2 to 15% propylene glycol alginate, and (c) 40 to 80% of a pharmaceutical medicament.
A preferred composition herein includes: (a) 20 to 40%, (b) 4 to 12% and (c) 45-68%.
These compositions will achieve up to a 20-40% dissolution of the medicament within 2 hours, and the remaining 60-80% will achieve dissolution within 10 hours.
In accordance with the invention, the composition in the form of tablets or pellets will release a drug within a period of 12 hours.
In this invention, dissolution of poorly water-soluble drugs is controlled by the swelling/erosion properties of the composition; while for water-soluble drugs it is controlled by diffusion through the composition.
In a preferred form of the invention, the sodium alginate component is present in an amount of 20-40% by weight of the composition, the propylene glycol alginate is 4-12%, and the drug is present 45-68%; and dissolution of the drug is accomplished at a release rate of between about 0.175%/min and 0.2%/min.
The formulation herein may optionally be coated with one or more film formers, employing one or more plasticizers, and one or more solvents and other conventional coating ingredients.
A wide variety of medicaments, including basic, neutral and acidic drugs, which ordinarily are orally administered in tablet form can be used in the form of tablets prepared according to this invention. These include, for example, drugs of a basic nature drug such as adrenergic agents such as salts of ephedrine, desoxyephedrine, phenylephrine, epinephrine, salbutamol, terbutaline and the like, cholinergic agents such as salts of physostigmine, neostigmine and the like, antispasmodic agents such as salts of atropine, methantheline, papaverine and the like, curariform agents such as salts of chlorisondamine and the like, tranquilizers and muscle relaxants such as salts of fluphenazine, thioridazine, trifluoperazine, chlorpromazine, triflupromazine and the like, antidepressants like salts of amitriptyline, nortriptyline, and the like, antihistamines such as salts of diphenhydramine, chlorpheniramine, dimenhydrinate, tripelennamine, perphenazine, chlorprophenazine, chlorprophenpyridamine and the like, cardioactive agents such as salts of verapamil, diltiazem, gallapomil, cinnarizine, propranolol, metoprolol, nadolol, and salts of any of the following: antimalarials such as chloroquine and the like, analgesics such as propoxyphene, meperidine and the like, etc. Other neutral and acidic therapeutic agents having the same or different physiological activity can also be employed in pharmaceutical preparations within the scope of the present invention.
Drugs can be in various forms, such as uncharged molecules, components of molecular complexes, or non-irritating pharmacologically acceptable salts, e.g. the hydrochloride, hydrobromide, sulphate, phosphate, nitrate, borate, acetate, maleate, tartarate, salicylate, etc. For acidic drugs, salts of metals, amines, or organic cations (e.g. quaternary ammonium) can be employed. Furthermore, simple derivatives of the drugs (such as ethers, esters, amides, etc.) which have desirable retention and release characteristics but which are easily hydrolyzed by body pH, enzymes, etc., can be employed.
The amount of drug incorporated in the carrier varies widely depending on the particular drug. The desired therapeutic effect, and the time span for which it takes the drug to be released. Since a variety of carriers in a variety of sizes and shapes are intended to provide complete dosage regimen for therapy for a variety of maladies, there is no critical upper limit on the amount of drug incorporated in the carrier. The lower limit, too, will depend on the activity of the drug and the span of its release from the carrier. Thus, it is not practical to define a range for the therapeutically effective amount of drug to be released by the carrier.
Preferred drugs to be incorporated according to the present invention are those designed for long-term treatment so that multiple daily doses can be avoided. For example, smooth muscle relaxants, e.g. theophylline, anabolics, e.g. methandrostenolone; analgesics, e.g. acetylsalicyclic acid, phenylbutazone or methadone; androgens, e.g. methyltestosterone; antibiotics, e.g. rifampin; antidepressants, e.g. imipramine or maprotiline; antidiabetics, e.g. phenformin; anticonvulsives, e.g. cabamazepine, antihistamines, e.g. tripelennamine; antihypertensives, e.g. hydrolazine; antinmfectives, e.g. trimethoprim; antiparasitics, e.g. nifurimox; antiparkinson agents, e.g. levodopa; antiph logistics, e.g. nap roxen; antitussives, e.g. benzostate; appetite depressants, e.g. mazndol; bronchodilators, e.g. fenoterol; coronary dilators, e.g. fenalcomine; corticoids, e.g. dexamethasone; cytostatics, e.g. floxuridine; diuretics, e.g. hydrochiorothiazide; hypnotics, e .g. glutethimide; neuroleptics, e.g. reserpine or thioridazine; psychoanaleptics, e.g. methylpenidate; tranquilizers, e.g. diazepam; uricosutics, e.g. sulfinpyrazone; vasodilators, e.g. isoproterenol.
Among the most preferred drugs are naproxen sodium, diclofenac sodium, baclofen, metropolol HCl, beta blockers, such as oxprenolol and propranolol; calcium channel blockers, such as Nifedipine and Verapamil, and anti-asthmatics, such as theophylline.
The composition optionally can contain excipients such as fillers, lubricants, binders and the like.